Process for producing hydrogenated alkyl tars

ABSTRACT

THIS INVENTION RELATES TO A PROCESS FOR THE PRODUCTION OF HYDROGENATED ALKYL TARS COMPRISING THE STEPS OF DESULFURIZATION AND ALKYLATION WITH A LOWER OLEFIN IN THE PRESENCE OF A CATALYST, OF A TAR FRACTION OBTAINED BY THE THERMAL CRACKING OF PETROLEUM HYDROCARBON AT A TEMPERATURE BETWEEN 700*C. AND 2300*C., FOLLOWED BY HYDROGENATION OF THE RESULTING ALKYL TAR IN THE PRESENCE OF A SUITABLE HYDROGENATION CATALYST.

United States Patent 3,600,298 PROCESS FOR PRODUCING HYDROGENATED ALKYL TABS Osamu Mayumi, Chiba, and Masaaki Takahashi, Tokyo, Japan, assignors to Kurelia Kagaku Kogyo Kabushiki Kaisha, Tokyo, Japan No Drawing. Filed Mar. 30, 1970, Ser. No. 23,962 Claims priority, applicatiorgggpan, Mar. 28, 1969,

rm. or. doc 1/20 US. Cl. 20844 9 Claims ABSTRACT OF THE DISCLOSURE The present invention is concerned with a novel process for the production of a mixture of alkylated naphthene compounds.

The process of this invention is also directed to the elficient utilization of heavy cracked oil by-products which are being produced in increasing amounts as the result of increased ethylene manufacturing operations.

After extensive study of the properties and utilization of tar fractions obtained in the high temperature cracking of petroleum hydrocarbons, applicants have now found that such tar fractions are polycyclic aromatic compounds having extremely few side chains, and that impurities initially present in the petroleum oil, such as sulfur, nitrogen, oxygen, metals, etc. are incorporated into the gas or pitch produced during the thermal cracking operation, thereby leaving a tar fraction containing greatly reduced amounts of such impurities. As the result of the above investigations, we have devised a method of reacting such tar fractions with an olefin and hydrogenating the resulting alkylated tar to thereby effect naphthenation thereof and to produce useful products.

The tar fraction employed as the feed material in this invention is obtained by thermally cracking petroleum hydrocarbons at a temperature of 700 C. to 2300 C., removing solid pitch from the heavy cracked oil, and is a fraction having a boiling range of 200 C. to 500 C calculated a normal atmospheric pressure.

It has been determined that the tar fractions, after inspection of their physical properties by gas chromatography, infrared absorption analysis, nuclear magnetic resonance analysis, mass spectrographic analysis, etc. are primarily polycyclic aromatic compounds having a struc ture consisting mainly of 2 to 5 aromatic rings, particularly 2 to 4 condensed aromatic rings substantially free from side chains. The intermediate alkylated tar of the present invention consists mainly of alkylated polycyclic aromatic compounds and the hydrogenated alkylated tar product of the present invention mainly consists of alkylated polycyclic naphthenes.

In carrying out the process of this invention, petroleum hydrocarbons are first thermally cracked at a temperature between 700 C. and 2300 C. to form olefins, such as acetylene, ethylene, propylene and butylene, together with heavy cracked oil. The petroleum hydrocarbons employed as feed include gaseous hydrocarbons, naphtha, kerosene, light gas oil, heavy gas oil, residual oil, mixtures of two or more of these, as well as crude oil. The thermal cracking may be carried out according to any conventional manner including flame cracking, high temperature steam cracking, ordinary steam cracking, etc.

The tar fractions to be used as the feed material to the process of this invention are those obtained from the heavy cracked oil after removal of the solid pitch contained therein, and have a boiling point range of from 200 C. to 500 C., preferably 250-450 C., calculated at normal atmospheric pressure. This tar fraction has a hydrogen to carbon atomic ratio (H/C) of from 0.5 to 1.0 and a specific gravity of from 1.0 to 1.3.

Though the tar fraction may be directly reacted with olefin, it is more effective to carry out preliminary desulfurization of the tar fraction, so as to lengthen the life of the alkylation and hydrogenation catalysts. The desulfurization may be conducted in any conventional manner using any known desulfurizing apparatus. Catalysts which may be employed in such desulfurizations include cobalt, molybdenum, or nickel as their metals, oxides, sulfides or combinations thereof, which may be employed on suitable carriers, such as alumina and silica-alumina. The desulfurizing reaction may be carried out at a temperature of 350450 C. under a pressure of 20-100 l :g./cm. using a feed ratio (molar ratio of hydrogen to tar) of 315 mole/mole, at a L.H.S.V. (liquid volume of reactions per hour per unit of catalyst volume) of 0.510 cc./cc. of cat/hr. Under such conditions, reaction takes place readily and good desulfurization of the tar fraction is obtained.

The following alkylation reaction of the present invention may be conducted by mixing gaseous olefin with the tar fraction and reacting them in the presence of a suitable catalyst. The catalyst employed is preferably a silicaalurnina type, or a catalyst comprising a Group III-B metal, such as lanthanum (La), cerium (Ce), thorium (Th), etc., employed on a zeolite carrier.

The olefin feed is preferably a lower olefin, generally having not more than 8 carbon atoms, preferably containing from- 2 to 4 carbon atoms. Typical of such olefins which may be used in the present invention are ethylene, propylene and butylene and the use of these olefins is economically advantageous. The reaction conditions which may be employed include a temperature of about 250 C. to 380 C., a pressure of about 1 to 50 -kg./cm. a feed ratio of about 0.2 to 10 mole of olefin per mole of the tar fraction and a liquid hourly space velocity of from 0.1 to 5.0 cc./ cc. of catalyst/hr. The reaction takes place readily over a prolonged period of time without substantial decrease of catalyst activity.

Since the components of the tar fraction of the present invention have very few side chains, the amount of alkyl side chains introduced may be controlled as desired. The length of the alkyl side chain added is dependent upon the kind of olefin used. The degree of alkylation (the moles of olefin reacted per mole of the tar fraction components) can be increased by either employing high feed ratios or using a small liquid hourly space velocity. The alkylated tar thus formed has a lower specific gravity, a lower refractive index, as well as higher H/ C values, viscosity, average molecular weight and boiling point than that of the feed tar fraction. Analysis of the alkylated product by gas-chromatography, infrared absorption spectrum, nuclear magnetic resonance analysis, etc., shows that the alkylated tar consists of condensed polycyclic aromatic compounds having from two to five, particularly from two to four, aromatic rings, which condensed ring compounds are combined with the added alkyl groups containing the same number of carbon atoms as that of the olefin used in the alkylation reaction.

The subsequent hydrogenation reaction is carried out by admixing the alkylated tar with hydrogen and reacting the mixture in the presence of a suitable catalyst. The catalyst which may be used in the hydrogenation includes Group VI, VII and VII metals, oxides, sulfides and combinations thereof, or such materials on carriers, such as diatomaceous earth, alumina, bauxite, pumice stone, silica-alumina, activated carbon, etc. Typical examples of such catalysts are nickel-diatomaceous earth, molybdenum-alumina, platinum-alumina, cobalt-nickel-alumina, etc. The reaction conditions which may be used include a temperature of 100-450 C., a pressure of 10-30 kg./cm. a feed ratio of 5-30 moles of hydrogen per mole of alkylated tar, a liquid hourly space velocity of 05-10 cc./ cc. of catalyst/hr. The reaction in this step mainly involves the hydrogenation of the polycyclic aromatics and is not accompanied by side reactions such as dissociation of the alkyl side chain, ring opening of the napthene rings, decomposition, polymerization, etc. Thus, the alkylated polycyclic naphthene compounds are formed in good yield. The degree of hydrogenation can be controlled by varying the reaction conditions, such as the liquid hourly space velocity. The reaction takes place readily under the above conditions, without appreciable deactivation of the catalyst, which can therefore be used over a long period of time. The hydrogenated alkyl tar so formed has a lower specific gravity, viscosity and refractive index and a higher H/ C than that of the alkylated tar before undergoing hydrogenation. Measurement of the physical properties of the hydrogenated product by the use of the above-mentioned analytic methods shows that the product consists primarily of compounds in which the alkyl group is attached to naphthene rings having from two to five condensed rings, particularly from 2 to 4 condensed rings.

As described hereinabove, this invention provides a process whereby hydrogenated, alkylated tar can be produced by adding alkyl groups under controlled conditions to the tar fraction consisting of polycyclic aromatic compounds having a few side chains and by thereafter hydrogenating the aromatic nuclei. Accordingly, various hydrogenated alkylated tars having the most desirable properties depending upon the intended use can be freely produced by the process of this invention.

The hydrogenated, alkylated tar products of this invention can be used in a variety of industrial fields, for example, as electric insulating oils, rubber processing oils, plasticizers, lubricant oils, heat-transfer oils, high energy fuels, special solvents, paints and intermediates in the production of various chemicals and possess outstanding properties which have never before been obtained.

4 EXAMPLE 1 Petroleum naphtha was thermally cracked by a flame cracking process at a temperature of 1200 C. and at a contact time of 0.003 second to obtain heavy cracked oil from which a relatively lower boiling tar fraction having a boiling point of 250-350 C. (at normal atmospheric pressure) was obtained by distillation under reduced pressure and used as the feed stock. The characteristics of this fraction are set forth in Table 1. The physical properties of the thus obtained fraction were determined by means of gas-chromatography, infrared absorption analysis, nuclear magnetic resonance analysis, mass spectrograph analysis, etc. to determine its chemical structure. The results of such analysis showed the tar fraction to mainly consist of aromatic compounds having from two to three condensed aromatic rings, said rings having very few methyl side chains attached thereto. This tar fraction was catalytically desulfurized with hydrogen. The desulfurization conditions are shown in Table 1. The olefin feed to the subsequent alkylation step was ethylene having a purity of 99%. The reactor used was,

a stainless steel tube of 1000 mm. in length and mm. in diameter and packed with a catalyst. The alkylation catalyst was granular silica-alumina (SiO 87%, A1 0 13%). The alkylation reaction was carried out by passing the tar fraction over the catalyst together with ethylene as a mixture. The reaction conditions, the properties of the feed tar fraction and the properties of the resulting (ethylated) tar are shown in Table 1. The reaction took place with ease and no substantial lowering of the catalyst activity was observed. In this case, the degree of alkylation varied as shown in Table 2 depending upon the change in the material feed ratio or liquid hourly space velocity, holding other conditions unchanged. The degree of alkylation can be increased either by employing feed ratio or by employing a smaller liquid hourly spaced velocity.

The ethylated tar was then hydrogenated. The hydrogenation reactor was a stainless steel tube of 2000 mm. in length and mm. in diameter and was packed with a catalyst comprising nickel by weight) supported on alumina (60% by weight). The reaction was conducted by admixing the ethylated tar with hydrogen and passing the resulting mixture over the catalyst bed. The reaction conditions and properties of the hydrogenated cth ylated tar are given in Table 1. The reaction proceeded with ease and without appreciable lowering of catalyst activity. By dropping the liquid hourly space velocity as shown in Table 3, the H/ C became greater indicating the TABLE 1.-ETHYLA1ION AND I'IYDROGENATION OF TAR FRACTION Reaction conditions:

Catalyst Temperature C Pressure (kgJemfl) Feed ratio 0..

Properties:

Specific gravity (15 C Refractive index (25 C.) Viscosity (20 0.), ep Average mol. wt Boiling point (V01. C Sulfur (wt. percen t alkylation degree (mole/mole) (reacted ethylenc/tar) 1 Co (5)-Mo (5)-alumina (90). 2 Silica (SD-alumina (13). 3 Nickel (40)-a1u1mna 4 Feed ratio: Desulfurization (moles hydrogen/moles tar fraction); alkylation (moles ethylene/moles tar traction); hydrogenation (moles hydrogen/moles alkylated tar).

[Temperaturez 300 0.; pressure: 30 kgJemfl; catalyst: silica (87 wt. percent), alumina (13 wt. percent)] Feed ratio 1 L.l'I.S.V. (ca/cc. at eat./hr.) Alkylation degree (mole/mole) 1 Moles ethylene/moles tar fraction.

The desulfurized tar fraction was then subjected to alkylation and successive hydrogenation in the same manner as in Example 1. The reaction conditions and the properties of the feed and the product are each given in Table 4. It will be noted that the hydrogenated ethylated tar can be readily produced from a high boiling tar fraction as well, and the reaction can be smoothly carried out Without substantial difficulty regarding the activity of either alkylation or hydrogenation catalyst even when using feed tar fractions containing a relatively high sulfur content, as long as preliminary desulfurization is conducted.

TABLE 4.-DESULFURIZATION, ALKYLATIgIfiIAEJE ITIPKISLATION) AND HYDROGENATION OF TAR Feed material Alkylation Hydrogen- (tar fraction) Desuliurization (ethylation) ation Reaction conditions:

Cat 1 st a y Temperature (1.). I

Pressure (kg/emi Feed ratio 4 L.H.S.V. (cc. Property:

Specific gravity C.)

Refractive index C.) Boiling point (vol. 50%) C.) gulur (percent by weight) 1 Co (ID-Ni (7)/Al Oi (90).

3 Ni diatomaeeous earth (60).

4 Same as footnote 4 in Table 1 above.

TABLE 3.-VARIATION OF H/C WITH CHANGING LIQUID HOURLY SPACE VELOCITY [Temperature: 250 0.; pressure: 100 kgJemJ; feed ratio (hydrogen/ alkylated tar): 10 mole/mole; catalyst: nickel (40 wt. percent), alumina (60 wt. pereent)] L.H.S.V. (co/co. at eata1yst/hr.) H/C EXAMPLE 2 EXAMPLE 3 Kuwait crude oil was thermally cracked by high temperature steam cracking at a temperature of 1000 C. for a contact time of 0.005 second to give heavy cracked oil which was distilled to give a tar fraction boiling at 250-450 C. (at normal atmospheric pressure) for use as the feed material. The properties of the tar fraction so obtained were as shown in Table 5. The relatively large proportion of sulfur initially contained in the amount of 2.05% by weight was reduced to 0.005% by weight by the desulfurizing treatment carried out under the conditions given in Table 5. The desulfurized tar fraction was then successively alkylated and hydrogenated in the same manner as in Example 1. The reaction conditions and the properties of the feed materials and products used are given in Table 5. The reaction proceeded smoothly to form hydrogenated ethylated tar. The activity of the alkyl-' ation and hydrogenation catalysts was unaffected even when using the tar fraction with this relatively high sulfur content of 0.224% by Weight which was higher than that content so long as it is preliminarily desulfurized.

TABLE 5 Feed material Alkylation Hydrogen- (tar traction) Desulfurization (ethylation) ation Reaction conditions:

at yst (1) (2) (3) Temperature C.) 400 350 250 Pressure (kg./cm. 50 40 150 Feed ratio 4 0.5 10 1O L.H.S.V. (cc./cc.-eat./hr.) 0. 5 1 0. 5 Prorertyzf t (15 C peer 1c gravi y 1. 040 Refractive index (25 0.). 1.650 goging point (v01. 50%) 410 365 1.05 1. Alkylation degree (mole/mole) (ethylene reacted/tar fraction) 1. 95 .f?

1 C0 (3)-Ni (7)/Alz0a (90). 2 Th (1.5)lzeolite (98.5). 8 Mo (15)/A1203 (85). I 4 Same as footnote 4 in Table 1 above.

of the tar fraction of Example I, which was obtained frompetroleurnnaphtha and contains 0.72% sulfur by weight. The tar fraction of this example was subjected to desulfurization treatment. The desulfurizing conditions I and results thereof are given in Table 4 which demonstrates the reduction of the sulfur content to below 0.001% by weight.

EXAMPLE 4 and product are given in Table 6. The reaction took place with ease to produce hydrogenated propylated tar.

The lighter fraction of the hydrogenated propylated tar is especially suited for use as a heat transfer oil and TABLE 6.PROPYLATION AND HYDROGENATION OF TAR FRACTION Feed material Alkylation Hydro- (tar fraction) (propylation) genation Reaction conditions:

Oat y Temperature 0.).-. 300 150 Pressure (kg/cm?) 40 50 Feed ratio 3 8 20 L.H.S.V. (cc./cc.cat./hr.) 1.5 1.0 Property;

Specific gravity (15 0.). 1.075 1.022 0.900 Refractive index (25 0.) 1. 643 1. 635 1. 487 Boiling point (vol. 50%). 300 382 350 I-I/C 0.85 1.15 1. 88 Alkylation degree (mole/mole) (propylene reacted/tar fraction) 2. 15

1 Silica (87)-alurnina (l3). 2 Platinum (1) lalumina (09).

3 Feed ratio: Alkylation (moles propylene/moles tar fraction); hydrogenation (moles hydrogen/moles alkylated tar.

EXAMPLE Using the same desulfurized tar fraction as in Example 1, the alkylation was carried out using butylene followed by hydrogenation in the same manner as in Example 1. The reaction conditions and the properties of the feed and product are given in Table 7. The reaction a special solvent, and the heavier fraction is suitably used 20 as an electric insulating oil and as a rubber processing oil, etc.

What is claimed is:

1. A process for the production of hydrogenated alkylated tar which comprises desulfurizing a tar fraction in proceeded smoothly to produce hydrogenated butylated 25 the presence of hydrogen and a desulfurization catalyst,

tan reacting a lower olefin with the desulfurized tar fraction TABLE 7.-BUIYLATION AND HYDRO GENATION OF TAR FRACTION Feed material Alkylation Hydro- (tar fraction) (butylation) genation Reaction conditions:

Cata (1) 2 Temperature 0.)... 300 200 Pressure (kg./cm. 50 100 Feed ratio 3 10 L.H.S.V. (ec./cc.-cat.lhr.) 3.3 1.0 Property:

Specific gravity (15 0.)-.. 1.075 1.018 0. 800 Refractive index C.) 1. 643 1. 630 1. 485 Boiling point (vol. 50%). 300 395 370 11/0 0.85 1. 1. e5 Alkylation degree (mole/mole) (butylene reacted/ tar fraction) 250 l Silica (SD-alumina (13). 2 Cobalt (5)-nickel (10)/a1umina (85).

3 Feed ratio: Alkylation (moles butylene/rnoles tar traction); hydrogenation (moles hydrogen/moles alkylated tar) EXAMPLE 6 Petroleum naphtha was thermally cracked by steam heating at 850 C. for 0.5 second to give bottom oil as the by-product in ethylene and propylene production. The bottom oil so obtained was desulfurized, propylated and then hydrogenated at the nuclei to produce hydrogenated propylated tar. The reaction conditions are given in Table 8.

TABLE 8.DESULFURIZATION, PROPYLATION AND HY DROGENATION OF BOTTOM OIL Alkylation Hydro- Reaction conditions Desulfuiization (propylation) genation Catalyst Temperature C.) 400 300 280 Pressure (kg/cm!) 50 100 Feed ratio (mole/mole) 2. 5 20 10 L.H.S.V. (cc./cc.-cat./hr.) 0. 5 1. 0 0. 5

l 00 (ED-Ni (7)/alumina (90). 1 Si 1 s7 8 Ni (4(i)-kieselguhr (60).

The so-formed hydrogenated propyl tar was divided into lighter and heavier fractions and the properties of each are set forth in Table 9 below:

in the presence of a catalyst to produce alkylated tar, and then hydrogenating the alkylated tar in the presence of a suitable catalyst, said tar fraction consisting essentially of polycyclic aromatic compounds and having been obtained by the thermal decomposition of petroleum hydrocarbons at a temperature of 700 C. to 2300 C.

2. The process of claim 1 in which the alkylation is carried out at a temperature of 250-380 C., a pressure of 1-50 kg./cm. a molar ratio of olefin to tar of 0.2-10 and an L.H.S.V. of 0.1-5 cc./cc.-cat./hr.

3. The process of claim 2 in which the alkylation reaction is carried out in the presence of a silica-alumina catalyst.

4. The process of claim 2 in which the alkylation reaction is carried out in the presence of a catalyst comprising a Group III-B metal on a zeolite support.

5. The process of claim 2 in which the olefin contains from 2 to 8 carbon atoms.

6. The process of claim 5 in which the olefin is ethylene, propylene or butylene.

7. The process of claim 1 in which the hydrogenation is carried out at a temperature of -450 C., a pressure of 50-150 kg./cm. a molar ratio of hydrogen to tar of 5-30 and an L.H.S.V of 0.5-10 cc./cc.-cat./hr.

8. The process of claim 7 in which the hydrogenation is carried out in the presence of a catalyst comprising a supported metal, metal oxide or metal sulfide of Group VI, VII or VIII.

9. The process of claim 1 in which the tar fraction has a boiling point range of ZOO-500 C., an atomic ratio of H/C of 0.5-1.0, a specific gravity of 1.0-1.3, and a struc- 9 W tural composition which consists essentially of aromatic OTHER REFERENCES hydrocarbons having from two to five rings. Chem & Eng News, VOL 34, N0 9, 46864 Sept.

References Cited 1956.

UNITED STATES PATENTS 5 DELBERT E. GANTZ, Primary Examiner 1,859,966 5/1932 Herthel 208-40 OKEEFE AsslstamExammer 2,970,099 1/1961 Illman 208-40 U.S. Cl. X.R. 3,453,202 7/ 1969 Friedman et a1 20844 260671 

